//	ID : pallab81
// 	PROG : 11857
// 	LANG : C++
// 	2011-09-12-07.57.02 Monday
//
// 	"I have not failed, I have just found 10000 ways that won't work.
//


#include <iostream>
#include <algorithm>
#include <vector>
#include <sstream>
#include <fstream>
#include <string>
#include <list>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <functional>
#include <bitset>

#include <ctime>
#include <cassert>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <climits>
#include <cstring>
#include <cstdlib>

using namespace std;

#define VI vector< int >
#define CI( x ) scanf("%d",&x)
#define CL( x ) scanf("%lld",&x)
#define CD( x ) scanf("%lf",&x )
#define fo(i,st,ed) for(int i = st ; i < ed ; ++i )
#define foE(i,st,ed) for(int i = st ; i <= ed ; ++i )
#define foit(i, x) for (typeof((x).begin()) i = (x).begin(); i != (x).end(); i++)
#define bip system("pause")
#define Int long long
#define pb push_back
#define SZ(X) (int)(X).size()
#define LN(X) (int)(X).length()
#define mk make_pair
#define f first
#define s second
#define SET( ARRAY , VALUE ) memset( ARRAY , VALUE , sizeof(ARRAY) )

inline void wait( double seconds ) {
    double endtime = clock()+( seconds* CLOCKS_PER_SEC );
    while( clock() < endtime ) {
        ;
    }
}

const int inf = (int)1e6;
int root[ inf+10 ];
int rank[ inf+10 ];
inline void _Set() {
    fo(i,0,inf) {
        root[i]=i;
        rank[i]=0;
    }
}
inline int _Find(int x) {
    if( x!= root[x] ) {
        root[x] = _Find(root[x]);
    }
    return root[x];
}
inline void _Union(int x, int y) {
    int rx = _Find(x);
    int ry = _Find(y);

    if( rank[rx] > rank[ry] ) {
        root[ry] = rx;
    } else {
        root[rx] = ry;
    }
    if( rank[rx]==rank[ry] ) {
        rank[ry]+=1;
    }
}
struct NODE {
    int x,y,cc;
    NODE( int a, int b, int c):
        x(a),y(b),cc(c) {}
};
inline bool cmp(NODE A, NODE B) {
    return A.cc < B.cc;
}
int n,edges;
vector< NODE > vt;
inline void Read() {
    vt.clear();
    int x,y,cc;
    fo(i,0,edges) {
        CI(x);
        CI(y);
        CI(cc);
        vt.pb( NODE(x,y,cc) );
    }

}
inline void Proc() {
    sort(vt.begin(),vt.end(),cmp);
    _Set();
    int min_cost=0;
    bool found=false;
    int i,j;
    for(i=0,j=0; i<edges && j<n-1; i++) {
        int x = vt[i].x;
        int y = vt[i].y;
        int cc = vt[i].cc;
        if( _Find(x)!=_Find(y) ) {
            _Union(x,y);
            ++j;
            if(found==false) {
                min_cost = cc;
                found=true;
            } else {
                min_cost = max(min_cost,cc);
            }

        }
    }
    if( j!=n-1 ) {
        printf("IMPOSSIBLE\n");
    } else {
        printf("%d\n",min_cost);
    }
}

int main() {
#ifndef ONLINE_JUDGE
    freopen("in.txt","rt",stdin);
#endif

    while( scanf("%d %d",&n,&edges)==2 ) {
        if(n==0 && edges==0)break;
        Read();
        Proc();
    }

    return 0;
}
